A giant beaver jaw from about 50,000 years ago was found in a gravel pit in southeastern Manitoba.
Dr. Graham Young is a curator of geology an paleontology at the Manitoba Museum. Young says the giant beaver or Castoroides ohioensis (species name) would have lived towards the end of the ice age, right before the glacier thawed and formed Lake Agassiz. He notes the giant beaver would have been much larger than a modern-day beaver and estimates it would have been the size of a bear.
Young notes it's an unusual find in Manitoba, in fact, this is only the fourth area in all of Canada where a giant beaver piece has been found.
"There have been three [other] documented occurrences in Canada. I think there's been quite a little bit found in the Yukon of this sort of creature. The other ones, that I know of, are single occurrences. One is the Don Valley brickyards in Toronto, not too far from the middle of Toronto nowadays. The other one was what is now an island right in the middle of the Bay of Fundy in New Brunswick."
He says, while all of these finds are quite spread out, there are other occurrences in the north-central U.S. including Minnesota, noting this find in Manitoba may be linked with the Minnesota occurrences.
2017 10 beaver2(Photo credit: Randy Mooi)Young estimates this piece is about 50,000 years old but he says those numbers are getting near the limits of carbon dating. He notes this particular piece has not been carbon dated, but they have tested other pieces found in the same area which are believed to be from the same time period. He adds this piece is almost certainly from the last 100,000 years.
"Carbon dating even now requires some destruction of a sample. It used to be quite a little bit and now it's a very small amount, but still, it's a lot easier to sacrifice a little bit of wood then to drill out part of a rare fossil bone."
Young says finding a piece like a jaw is much better for identifying the species.
"Of course it would be great to get the entire creature, but something like the jaw is really good because you can get an identification from it. So, for instance, we've had various other pieces from the area, there was a bison vertebra donated at the same time. With the vertebrae you can say 'yes, it looks to be bison' but you can't say what species because all bison have similar vertebrae. Whereas, if you get something like a jaw or part of a skull, you can actually say what species you have."
He explains the process a fossil goes through when donated.
"It very much depends on what you're getting. The trick or challenge with pieces that have come from places like the [Southeast] is that it's been soaked in water for many centuries so it needs to be dried out slowly. Even when you dry it slowly you'll get some cracking, so that's a substantial challenge, to dry it really slowly. With this particular piece, it ended up going to our conservation people who put it in a special bag with a monitoring device so they could monitor the humidity, the moisture content."
Young says their conservators have told them the piece is in their collections room where the humidity is kept quite high. He notes it's not something they could put on exhibit for months because the drying process can take a long time.
"It might need a special climate-controlled case because, as you know, buildings in Winnipeg tend to be really dry in the winter time. So, any of these bones that have come from places like that, they're okay in our collections room because it's maintained at a humidity of 30-something percent. But humidity is a fraction of that when you get out into buildings in Winnipeg, which is why things like musical instruments crack up. It's the same sort of issue with bones as with wood."
He notes there are a few theories as to why the giant beaver would have become extinct.
"There were a lot of big creatures that went extinct at about the same time," he says. "So, we're talking 10,000 to 12,000 years ago. This was the same time as mammoths, mastodons, the horses that were native to North America, and some of the ground sloths; so, a lot of the big things went extinct. It was that time of Lake Agassiz (when the glacier moved south to form the lake), it was the time that the climate was changing a lot and rapidly. We know that when we get climate change, a lot of creatures are stressed and populations shrink. They probably found it hard to find food. At the same time humans arrived. So, it's probably that whole combination of factors."
Young reiterates it was probably a combination of climate change, landscapes changing, declining food, and humans arriving. He adds humans are good at making use of food resources, so there were big creatures with lots of meat on them that could nicely feed a family.
He says, over the years, there have been several pieces found in the Southeast including many mammoth pieces, which he says are believed to be from the same time period as the giant beaver.
"They'd all be from the same general ice age period. Things come out of gravel pits and things in gravel were probably, somewhat transported before they were buried. I think it's kind of interesting that there have been quite a lot of ice age pieces come from southeast Manitoba over the years."
Young says he looks forward to more findings in the future.